This application claims the priority of German application No. 197 42 065.6, filed Sep. 24, 1997, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a shifting arrangement of a transmission, and more particularly, to an arrangement wherein at least two shift rods, which are aligned in parallel, are arranged in a housing in a displaceable manner in their longitudinal directions relative to one another as well as with respect to the housing and are provided with one clutch groove respectively for the engagement of a shift finger. In the neutral positions of their shift rods, the clutch grooves are aligned with one another in a selecting plane of the housing, and the shift finger, which is arranged immovably with respect to a shifting shaft disposed by means of its axis in the selection plane or in parallel to the selection plane as well as in a rotationally and axially displaceable manner in the housing, can be displaced by the shifting shaft to cause selecting movements in the selecting plane for its engagement in the clutch groove of the shift rod to be selected and to cause shifting movements in each case in a shifting plane of the housing which is situated transversely or perpendicularly to the selecting plane or approximately centrically with respect to the groove walls of the clutch groove arriving in an engagement with the shift finger.
EP 0 532 924 A2 shows a shifting arrangement for a synchronized speed change transmission of a motor vehicle, in which some forward speeds can be shifted by swinging forks, which engage in synchronizer clutches and are swivellably disposed in the transmission case. A shifting shaft is disposed in a longitudinally displaceable and rotatable manner in the transmission case parallel to the bearing axis of the swinging forks.
In order to construct this known shift mechanism at lower cost and in an operationally more reliable manner by reducing the number of component parts, this known shifting arrangement is further changed so that a shift finger is fastened to the shifting shaft which interacts with shifting lugs fastened to the swinging forks. By way of the shift finger's longitudinal displacement in the mutually aligned grooves of the shifting lugs, the gear speeds can be preselected and can be shifted by a rotation of the shift finger.
The known shift finger is surrounded by a locking bow and reaches through it. The locking bow is longitudinally guided in the axial direction of the shifting shaft, being locked in the rotating direction and resting against both faces of the hub of the shift finger. The locking bow is longitudinally guided in a guiding groove of the transmission case and is secured against a twisting. The locking bow forms a square which is closed with the exception of the passage opening for the shift finger. At this square, the concentric cross web, which connects the two radial legs, engages as a counterguide into the concentric guide groove of the transmission case.
The passage opening for the known shift finger is provided in the section of the locking bow disposed diametrically opposite the cross web with respect of the axis of the shifting shaft. The two concentric bow ends of the locking bow, which adjoin the passage opening, are constructed as a respective locking member. Because of this further change, the known locking bow forms a two-armed lever which, at a central point of its radial legs, is swivellably disposed with respect to the shifting shaft and has the locking members at the free end of its one lever arm and the counterguide at the free end of its other lever arm. Naturally such a further change is bulky and, in the case of a one-piece shifting shaft, disadvantageous with respect to the mounting, because a demounting of the locking bow is possible only after the opening-up of the connection between the shift finger and the shifting shaft.
In the known shifting arrangement shown in DE 36 02 157 A1 for change speed transmissions of motor vehicles, a shifting shaft is provided which can be rotated for preselecting shifting channels and can be axially displaced for engaging speeds and on which, by way of its hub, a shift finger is fastened and can selectively be engaged with grooves on shifting arms of shifting forks guided on the shifting shaft in order to select a shifting fork. A blocking plate guided on the shifting shaft is radially swivellable but axially fixed in order to block the not selected shifting forks with respect to a shifting movement. In order to provide a spring-loaded notched device for fixing the speed shifting position which, on one hand, avoids tolerance problems and which, on the other hand, by way of a minimum of constructional and mounting expenditures, can, in addition, provide a shifting boundary or a blocking plate fixing and a shifting boundary, the blocking plate hub in this known shifting arrangement reaches around the shift finger hub in a known manner and a cylinder projection is provided on the blocking plate hub for receiving a spring--ball notch and corresponding opposite detent indentations are constructed in the shift finger hub.
In a first embodiment of this known shifting arrangement, an axial slot is provided in the shift finger hub, opposite which a bore is arranged in the blocking plate hub. The bore receives a pin which extends radially toward the inside and which projects into the axial slot while limiting a shifting movement. In a second embodiment, a rectangular opening is provided in the shift finger hub above which a blocking slot is arranged in the blocking plate hub. This blocking slot extends in the circumferential direction, and a blocking bolt with a pin end is arranged in the transmission case. The pin end extends radially through the blocking slot as well as into the rectangular opening.
In the additional known shifting arrangement shown in DE 42 42 456 C2, a manual shifting lever is cardanically suspended in a so-called shifting dome of a shift control housing by a joint support. Thereby, the manual shifting lever can be swivelled about a swivelling axis fixed in space with respect to the shifting dome for the selection of the shift rods and about a second swivelling axis fixed in space with respect to the joint support for operating the respective selected shift rod. A block support part, which at a distance encloses the shift finger constructed in one piece with the lower end of the manual shift lever, projects from the joint support.
The block support part in this additional arrangement has, on its face situated at the same level with the shift finger, two stop cams situated on both sides of the shift finger for engaging in the shift groove of a shift rod which in each case is not selected. While the shift finger is arranged immovably with respect to the joint support by way of the pertaining uniaxial joint in the directions of the selecting plane and is swivellably movably arranged in the directions of the respective shifting plane, by way of the cardanic bearing of the manual shifting lever and the additional development of the cardan joint as a block carrier for the blocking of the not selected shift rods, this shifting arrangement requires relative large amounts of space and results in high costs.